1. Field of the Invention
The present invention relates to methods for preparing useful peptides, and more particularly to solution synthesis methods for preparing H-ARG-X-Z-Y-TYR-R and to compositions useful therein.
2. Description of the Prior Art
In U.S. Pat. No. 4,190,646 and U.S. patent application Ser. No. 124,959, filed Mar. 13, 1980, there are disclosed various peptides which are useful in thymic function and immunological areas. The patent discloses the "thymopoietin pentapeptide" (TP5) and substituted derivatives thereof, while the application discloses peptide analogs of TP5 which have greater potency than TP5. This patent and patent application are incorporated herein by reference. In the referenced patent and application, the peptides were prepared by solid-phase synthesis techniques commonly described as "Merrifield Synthesis." The patent and application also disclose that classical techniques (i.e., solution synthetic techniques) may be employed to prepare certain of these materials, but no specific classical method or synthetic route was disclosed.
While the solid phase synthetic technique of Merrifield is a convenient one for preparation of small quantities of peptides in the laboratory, it would be impractical and generally uneconomic for preparation of large quantities (e.g., more than about 100 grams) of peptide, for which solution synthetic techniques are more appropriate. Moreover, solution synthesis techniques are generally much less costly than solid-phase techniques due to the much lesser unit cost of certain of the reagents used. Among the large variety of solution synthetic techniques available for use in polypeptide preparation, Applicants have discovered particular synthetic methods which produce the desired peptide conveniently and economically.